Fuel injector pump for internal combustion engines



2,366,771 FUEL INJECTOR PUMP FOR INTERNAL-COMBUSTION ENGINES I H. DA COSTA Jan. 9, 1945.

Filed April 18, 1942 2 Sheets-Sheet 2 Patented Jan. 9, 1945 FUEL mmcron ruMPFon INTERNAL- comnus'rron enemas Harry da Costa Londo n, England, asslgnor to The 'Plessey CompanyLimited, Ilford, land, a British company Essex, Eng- Application April is, 1942, Serial No. 439,516

In Great Britain April 18, 1941 i 3 Claims. (01. 103-38) This invention relatesto liquid injection pumps and is particularly applicable to fuel injection pumps for injecting accurate quantities of liquid fuel into the engine or to that part of the engine to which fuel is normally tobe supplied. In injectionpumps of the more usual kind the quantity of fuel pumped at each stroke depends upon the co-operation betweenthe pump plunger and a port or ports in the cylinder in which the plunger is reciprocated. 'In consequence very precise setting of the pump plunger 'lnthe cylinder is necessary and, furthermore, theedge of the port which provides the requisite cut-off in con junction with the plunger must be accurately maintained. An object of ,the PIBSGHtLiI'lVGD-tiOIl is to provide a pump in which the disadvantages of accurate relationship; between the plunger and the port opening islavoided, and the invention is applied to that type of injection pump in which the pump plunger is soformed as to comprise through the pump outlet.

According to lthe present invention a pistonand cylinder liquid, injection pump comprises in within it a liquid receiving chamber bymeans of i which liquid received within, it is, discharged combination. a pump cylinder, inlet and outlet,

.ports opening into said cylinders at positions spaced axiallyapart in the wall thereofya reciprocating' pump plunger having in ita fuel chamher. which, during a stroke of the plunger, is

moved from a position in which it communicates with the inlet port to a'position in which it communicates with the outlet port; and means asso ciated with said chamber. for expelling part at least of the charge containedtherein through the outlet-port. i i

More particularly, a pump according to the invention' comprises in combination a pump cylinder, inlet and outlet ports opening into said cylinder at positions spaced axially apart in .the wall formed in two co-operating and axially aligned portions which provide between them a collapsable liquid receiving chamber, said chamber, being moved during a stroke of the plunger froma position in which it communicates. with the inlet port to a position in which it communicates with the outlet port, and means to cause relative approach of the twopiunger portions in .order to expel part at least of the charge contained in the saidchamber. i i

The pump is preferably. operated to reciprocate one of the parts ,of the plunger with a constant stroke, and a further. feature of the invention consists inthe provision for adjustmentof the means limiting the movement of the other part of the plunger inorder to vary the quantity of fuel delivered at eachstroke of the pump.

In order that the invention may be more clearly understood, one preferred example will now be described with the aid of the accompanying drawings, in which, i

Figures 1 and 2 illustrate one form oi the iiivention in two sectional views in planes atright angles to one another respectively, each section being in a plane containing the axis of the pump plunger:

Figure 3 is a fragmentaryvlew slmllarto Figure 1 of a modified form of the invention; and

Figure dis another sectional view similarto Figure 1, showing a stillfurther modification of the invention. 1 H

:Thepump body In, has a cylindrical bore ll of uniform diameter forming the pump cylinder in which the pump plunger l2, I3 is 'slidable. The

part P2 of the plunger projectsfrom one end of thecylinder and engages with arotary cam ll for reciprocating the plungeragainst. the action of a return spring [5. The cam I4 is secured. to aspindle l6 by ,which it is rotated. i 5

, The pump bodyfhas an inlet port I! and, an

outlet portl8 opening i nt o the pump cylinder and these ports are spaced apart, lengthwise of thecylinder, by a distance approximately equal to the stroke of the pump plunger.

The pump plunger formed in two parts l2 and I 3 previously referred to arranged end to end in axial alignment. The main part l2:which is actuated by means of the cam I4. is formedwlth a bore [9 in its upper end and receives in it the extreme end of a reduced portion or stem 2B of the other part l3 of the plunger. Stem 20 car thereof, a reciprocating pump plunger,

ries a transverse anchor pin 2| engaging at its ends length wise in slotsl? inthe main part 12 of the'plunger thereby enabling the part l3 to move relatively to partlZ to a limited extent.

, A coiled compression sprlng 23 isprovided surrounding the stem 20 and acts at its ends on the upper end ofthemain part .l2 vand on a shoulder 24 of thepart l3 so as normally to hold the two parts of the plunger separated to amaximum extent. The annular space formed in the plunger by provision of and surroundingstem 20 "constitutes the fuel chamber aforesaid, and, in

on extreme position of reciprocation of the plunger this chamberis opposite the, inlet port Hand at the other extreme, position is, opposite i the delivery port I BJQIn the uppenend of the cylinden; that isto ,say, that end adjacent the auxiliary part [3 of-the plunger, there'ls' screwthreaded a stop 25 for adiustably limiting the movement or stroke of the auxiliarypart I3 of the plunger.

by the two parts of the plunger in co-operation with the wall of the cylinder.

the auxiliary part I3 of the plunger is limited by the stop 25 while the main part of the plunger continues its full movement to the end. of the stroke. Thus, the two parts of the plunger are relatively moved against the action of spring 23 to reduce the volume of the fuel chamber and to deliver a portion of the fuel content in the plunger fuel chamber to the delivery port I8 past a nonreturn valve 26 provided therein. The quantity of fuel ejected from the pump by the above-described relative movement of the two parts of the plunger is accurately controlled by the position of the stop 25 and in consequence accurate deliveryof fuel through the delivery port I8 is obtalned on each stroke of the plunger.

Stop 25 instead of being screwthreaded into the pumpcylinder may consist of a cam I25 as illusv trated in Figure 3 or any other preferred means which serves adiustably to limit movement of the auxiliary part I3 of the plunger may be employed. In the case of a multiple pump unit for multicylinder engines, screwthreaded members such as 25, cams such as I25 or the like may be suitably interconnected for simultaneous control.

When this chamber has reached the delivery port movement of.

A vent 21 is provided for the cylinder beyond the outer end of the auxiliary part I3 of the plunger so as to prevent any fluid pressures being developed which would act upon this part of the plunger to tend to retard its movement.

Inlet ports I! may be arranged to communicate by way of thefuel chamber formed in the plunger with another port 28 displaced around the cylinder from theinlet port so that fuel may pass through the pump body by way of the fuel cham-- ber when the latter is in the appropriate position in order to feed a plurality of pumps mounted side by side. Alternatively, this additional port 28 may be employed as a vent or bleed in the case in which fuel is gravity fed to the inlet port.

In another alternative form, for instance, where viscous fuels are used, the fuel may be applied to the inlet port I1 under pressure by means of a pump and the additional port 28 may be utilised to provide a return for fuel to the pump so as to have a constant circulation of fuel in order to prevent air-locks from occurring.

In the foregoing examples of the invention, after delivery of the fuel andon the return stroke of the combined plunger I2, I3, the fuel space expands and, particularly in the case of light adjustable stop 25. In this case, however, a fuel inlet II! and a fuel outlet H8 are arranged in line with one another and are controlled by nonplunger is received and which has inlet and return valves H9 and I 20 respectively. A light spring 23 may be provided as before to tend always to maintain the two parts of the plunger separated to a maximum extent or, if desired, this spring may be omitted and the fuel feed pressure through the inlet I" may be relied upon to separate the two plunger parts immediately after a fuel injection operation has taken place.

With the construction Just described in connection with Figure 4, the cam I4 only reclprocates plunger I2, I3 "irough a very short stroke so that the fuel chamber surrounding stem 28 is never removed from its position of communication with the inlet Ill. In operation, as plunger I2 is lifted by cam I4 part I8 travels with part I2 until stop 25 is reached, whereafter the final movement of part I2 under the action of cam II elects fuel past non-return valve I28 through delivery conduit II8 to the engine and on the return stroke, immediately the parts I2 and I3 commence to separate further fuel is fed into the enlarging fuel each stroke of the plunger.- It is a further advantage of a pump according to this invention that alteration by adjustment of stop 25 in the quantity of fuel delivered on each stroke does not vary the finishing time of-the delivery, and any alteration in the quantity of fuel delivered is obtained by changing the position in the stroke of the plunger at which delivery commences.

I claim:

1. A piston-and-cylinder fuel-injection pump for internabcombustion engines, comprising in combination a pump plunger formed in two relatively axially movable parts providing between them a fuel chamber, a pump cylinder in which the two-partplunger is received and which has inlet and delivery ports communicating with the fuel chamber in the pump plunger, a spring housed within the cylinder and interposed between adjacent extremities of the two parts of the pumpplunger and normally tending to separate them to enlarge the fuel chamber to its full extent, and plunger actuating means serving to reciprocate the plunger and periodically to reduce the capacity of the chamber by effecting relative movement between th two parts.

2. A piston-and-cylinder fuel-injection pump for internal-combustion engines comprising in combination a pump plunger formed in two relatively axially movable parts providing between them a fuel chamber, means interconnecting the two movable plunger parts to permit axial movement between them to a predetermined limited extent, a pump cylinder in which the two-part delivery ports communicating with the :fuel chamber in the pump plunger, a spring housed within the cylinder and interposed between adjacent extremities of the two'parts of the pump plunger and normally tending to separate them to enlarge the fuel chamber toits full extent, and plunger actuating means serving to reciprocate the plunger and periodically'to reduce the capacity of the chamber by effecting relative movement between the two parts.

3. A piston-and-cyiinder fuel-injection pump for internal-combustion engines comprising in combination a pump barrel, a pump plunger formed in two parts sliding end to end within the barrel, means interconnecting the two plunger parts to permit axial movement between them to a predetermined limited extent, inlet and outlet delivery ports opening into the pump cylinder in the region of the pump chamber formed at the junction of the pump plungers, a springhoused within the cylinder and interposed between adjatit cent extremities of the pump plungers tending always to separate those ends, a spring operating on one of the plunger parts tendingto withdraw it and its companion part from the cylinder, an eccentric operating on the end of the plunger in opposition to the external spring and an adjustable stop limiting movement of the other plunger part in opposition to the movement imparted by the eccentric, all for the purpose described.

HARRY DA COSTA. 

